Heretofore, military aircraft have typically been provided with countermeasure devices to jam or distract radar, or to sink a missile onto a decoy. The devices for such countermeasures have included radar-jamming chaff, flares for generating heat to attract the guidance system of missiles, and mini-jammers which comprise active transponders. Such countermeasure devices have typically been maintained in a matrix of individual casings or cylinders receiving appropriate chaff, flare, or mini-jammer cartridges.
The countermeasure devices discussed above are actuated by the firing of an electro-explosive device or impulse cartridge uniquely associated with each of the individual cylinders. The electro-explosive device is actuated by a bridge wire which is heated by electrical current passing therethrough. When the bridge wire heats to a predetermined characteristic temperature, it ignites powder which forces the payload of chaff, flare, or mini-jammer out of the associated casing or cylinder. As is presently known in the art, the bridge wire will reach sufficient temperature for igniting the powder upon application of, for example, five amperes for fifty milliseconds.
Previously, firing of the various countermeasure devices from the matrix of the individual cylinder casings was achieved by means of a sequence switch. This switch consisted of a plurality of electromechanical rotary switches driven by solenoids pursuant to the program of a control processor. However, the electromechanical characteristics of the prior art switches gave rise to concern over issues of reliability, weight, packaging, and the like. Further, such switches have associated therewith a characteristically high electromagnetic interferences (EMI) and are rather expensive to produce.
For safety purposes, it is desired that the bridge wire of the electro-explosive device or impulse cartridge be shorted to ground until such time as the device is to be actuated or deployed. At that time, and at that time only, the short to ground would be removed and five amperes of current would be passed through the bridge wire for a fifty millisecond duration. Such shorting, removal of short, and current application are achievable using electromechanical rotary switches, and for that reason such switches have continued in use. However, as previously discussed, such switches have certain inherent drawbacks such as high EMI, cost disadvantages, and reliability problems inherent with electromechanical devices.